Proximity fuze



Jan. 9, 1968 K. O. G. LAGERSTRGM ETAL PROXIMITY FUZE Filed March 14,1966 INVENTORS KARL OLOF GUN/VAR LAaERsrRdM 6057:: um

KE 7 JOHN mEDR/K ALF HARTMA/V/V United States Patent Ofiice 3,362,331Patented Jan. 9, 1968 3,362,331 PROXIMITY FUZE Karl Olof GunnarLagerstrtim, Eskilstuna, Giista Wollre,

Jakobsberg, and John Fredrik Alf Hartmann, Stockholm, Sweden, assignorsto Forsvarets Fabriksverk,

Eskilstuna, Sweden Filed Mar. 14, 1966, Ser. No. 534,067 8 Claims. (Cl.102-702) ABSTRACT OF THE DISCLOSURE Proximity fuze in which anelectrical circuit for determining the firing sensitivit yof theproximity fuze includes a number of series or parallel connectedimpedance elements located inside the envelope of the fuze. Each of theimpedance elements have subsidiary circuits which include a melting fuzeand connectors from each end of the associated fuze which penetrate thewall of the envelope through insulation members providing electricalinsulation from the remainder of the envelope and from each other. Theconnection of each melting fuze and its associated impedance element inthe sensitivity circuit provides a predetermined impedance influence orabsence of such influence on the sensitivity circuit by the associatedimpedance element, which influence or its absence is changed by meltingof the associated meltab-le fuze. Terminal ends of each pair ofconductors are located at or just under the outer surface of theenvelope insulation on portions and an appropriate external currentsource can be temporarily applied to desired pairs of such terminals tomelt a specific meltable fuze to thereby change the impedance and hencesensitivity setting of the sensitivity circuit without gaining access tothe interior of the fuze.

Cross reference to related application Background The present inventionrelates to a proximity fuze for a projectile, such as a bursting shell,which makes the projectile detonate shortly before it hits the target.The proximity fuze radiates energy in the form of electromagnetic wavesor sound waves. A part of the radiated energy is reflected from thetarget returns to and is received by the proximity fuze. When thereceived energy reaches a predetermined level the fuze ignites thecharge in the projectile.

The amount of received reflected energy is greatly dependent on thereflecting power of the target. If the ground is the target, thereflecting power depends upon the character of the terrain andtherefore, the distance from the target at which a projectile with apre-set proximity fuze detonates, will -be different for different kindsof target terrain. The distance where detonation occurs is alsoinfluenced by the angle of the direction of movement of the projectilein conjunction with terrain surface, also by the speed of theprojectile, and whether or not there are woods on the target terrain.

The distance from the target at which detonation should take place, inorder to obtain the best possible eifect, is dependent on the protectinglevel of the target, on the angle between the direction of movement ofthe projectile and the target level and on the capacity of the terrainto prevent the spreading of splinters. For each type of projectile thedistance from the target at which detonation should occur, in order tocause maximum damage, has a specific value. The damage caused by theprojectile when exploded at the desirable specific distance isfrequently many times greater than if the projectile is exploded atother distances, which could be rather close to the specific distance.

Before each shot it may as a rule be possible to find out or to estimatethe reflecting power and the character of the terrain, such as thepresence of woods, and also the protecting level of the target. It mayalso be possible to know or estimate the speed of the projectile, theangle between the direction of movement of the projectile and the levelof the target, and also the specific explosion distance for maximumdamage. Therefore, it is possible to increase the eflfect of theexpenditure of ammunition if the proximity fuze of each projectile iscapable of being adjusted immediately before the firing, so that eachprojectile may explode at the desired specific distance and maximumdamaging effect will be obtained.

The adjustability may be continuous or non-continuous. Generally thecharacteristics of the fuze may be changed by adjusting an impedance,such as a resistance, in the electric circuit of the proximity fuze, forexample in its amplifier part. It is also possible to change themagnitude of the transmitted energy or to adjust the sensitivity of thereceiving means. If a continuous adjustability is wanted, for example inthe form of a continuously adjustable potentiometer, special steps haveto be taken to ensure a good contact-making in consideration of theforming of oxide on the contact-making parts during storage. Further,there should be a way to effectively prevent the adjustment of thepotentiometer from being influenced by the rotation of the projectile.There is a device known for this purpose (U.S. Patent 2,552,482) but itis rather complicated.

Summary Calculations have shown that it is sufficient to provide anadjustability of the characteristics of the proximity fuze in ten stepsor less, in order to obtain a correct adjustment of the distance atwhich detonation should take place for achieving the maximum damage.

One object of the present invention is to provide a proximity fuze whichis adjustable in steps. This adjustability means that thecharacteristics of the fuze may be altered in steps, so that the desireddistance from the target for detonation may be approximatively obtained.By a stepwise adjustment a simpler and more rigid construction can beobtained than by a continuous adjustability.

Another object of the invention is to provide such a stepwiseadjustability by enabling an impedance to be adjusted without any needfor disassembling the fuze or to make any incision in the fuze or toinfluence the aerodynamic characteristics of the projectile.

A further object resides in the provision of a proximity fuze accordingto the invention having a number of series-connected orparallel-connected impedance elements, the elements being connected in asensitivity-determining electrical circuit of the proximity fuze, andconnected to conductors which penetrate the envelope of the fuze and areinsulated from the envelope by insulation members, the ends of theconductors being located at or just under the outer surface of theassociated insulating members and such outer surface being in level withthe outer surface of the rest of the envelope, a melting fuse beingconnected between two conductors belonging to each impedance element.

Further objects and features of the proximity fuze according to theinvention will become apparent from the 3 following description andclaims and from the accompanying drawing, in which:

FIG. 1 illustrates a circuit diagram for a part of an electricalsensitivity-determining circuit of the fuze in which a plurality ofimpedance elements are connected in series;

FIG. 2 is a simplified section through the proximity fuze, showing oneof the impedance elements and its associated melting fuze as in thecircuit of FIGURE 1; and

FIG. 3 is a circuit diagram of a second embodiment and illustrates apart of an electrical sensitivity-determining circuit of a proximityfuze in which a plurality of impedance elements are connected in series.

FIGURES l and 2 represent an embodiment where a number of impedanceelements 1 are connected in series with each other and form a part of anelectrical sensitivitydetermining circuit, for example a potentiometer(not shown). Each impedance element 1 is located inside the envelope 2of the fuze and is connected to conductors 3 which penetrate the wall ofenvelope 1. Conductors 3 are insulated from the envelope wall byinsulation members 4.

Each impedance element 1 is shunted by a melting fuze 5. Each end ofeach melting fuze 5 is connected to one of the conductors 3 whichpenetrate the wall of the envelope 2. The terminating end of eachconductor 3 is located just at the exterior surface of the insulatingmember 4, and is preferably terminated by a plate-shaped member 6.

When it is desired to connect or activate one of said impedance elementsin order to change the sensitivity circuit characteristics of theproximity fuze, the associated melting fuze 5 is blown by temporarilyapplying a current source to the ends of the associated conductors 3.This is accomplished from the outside of the fuze and no disassemblingof the proximity fuze or other incision in the latter is necessary.

In the second embodiment, represented by FIGURE 3, the impedanceelements 1' and 1", as an example, are connected in parallel instead ofin series as shown in FIGURE 1. YVhen they are connected in parallel, amelting fuse, respectively, 5 and 5", should be connected in series witheach impedance element, respectively, 1' and 1". Each end of eachmelting fuse, 5 and 5" should be connected to an associated conductorwhich, in insulated relationship, penetrates the wall of the envelope2'.

As illustrated in FIGURE 3, branch conductors and 10 from one end ofrespective melting fuzes 5' and 5" penetrate the envelope 2 throughrespective insulated portions 11 and 11' and branch conductors 12 and 12from the other end of respective melting fuzes 5 and 5" penetrate theenvelope 2; through respective insulated portions 13 and 13. All of theconductors 10, 10, 12 and 12 terminate in respective plate-shapedmembers 14, i5, 16 and 17, similar to members 6 described for FIG- URE2. An appropriate level current source, temporarily applied to a pair ofterminals such as 14 and 15 or 16 and 17, will cause the melting fuzeassociated with the selected pair of terminals to melt, whereupon theconnection of the associated impedance element 1' or 1" in the impedancecircuit of the sensitivity circuit is disrupted or opened.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

We claim:

1. In combination in a proximity fuze which comprises an envelope and anelectrical circuit for determing the firing range sensitivity of theproximity fuze, the improvement comprising: a plurality ofinterconnected impedance elements located inside of said envelope andconnected in said sensitivity circuit; and a plurality of subsidiarycircuits, each of which is associated and connected in circuit with aspecific one of said impedance elements in said sensitivity circuit sothat continuity of each of said subsidiary circuits controls the etfectof its associated impedance element on the impedance of the sensitivitycircuit; each of said subsidiary circuits including conductor meanspenetrating said envelope and having portions located immediatelyadjacent the envelope exterior surface; the portions of said envelopepenetrated by said conductors constituting elecrically insulating meanswhich insulate said conductor terminal portions; said conductor portionsand their associated subsidiary circuits providing exteriorly accessiblecontrol means by which the impedance effect of each of said impedanceelements on said sensitivity circuit can be changed.

2. The combination as defined in claim 1, wherein each of saidsubsidiary circuits includes a melting fuze and conductors, one fromeach end of said melting fuze, having terminal portions penetrating saidenvelope and terminating immediately adjacent the envelope exteriorsurface; said pairs of conductor terminal portions and their associatedmelting fuzes providing said exteriorly accessible control means bywhich the impedance effect of each of said impedance elements on saidsensitivity circuit can be changed.

3. The combination as defined in claim 2, wherein said plurality ofimpedance elements are connected in series with each other in saidsensitivity circuit, and each of said subsidiary melting fuze circuit isshunt connected across an associated said impedance element.

4. The combination as defined in claim 2, wherein said plurality ofimpedance elements are connected in parallel with each other in saidsensitivity circuit, and each of said subsidiary melting fuze circuitsis connected from one end of and in series with an associated saidimpedance to one side of said parallel connection.

5. The combination as defined in claim 2, wherein said conductorportions penetrate into and through said envelope and a terminal plateis connected to the terminal end of each conductor portion andaccessible at the exterior surface of said insulating means.

6. The combination as defined in claim 2, wherein said conductorportions which penetrate said envelope are embedded in said insulatingmeans with the terminal ends thereof closely adjacent but below theexterior surface of said insulating means.

'7. The combination as defined in claim 2, wherein the exterior surfaceof said insulating means is smoothly contoured with the exterior surfaceof the remainder of said fuze envelope.

8. The combination as defined in claim 2, wherein the terminating endsof said conductor portions are connected to terminal devices.

References Cited UNITED STATES PATENTS 2,552,482 5/1951 Ferris et al10270.2 3,001,476 9/1961 Boykin 10270.2 3,048,136 8/1962 Holmes 10270.2X 3,166,015 1/1965 Tuve et a1. 7.02

BENJAMIN A. BORCHELT, Primary Examiner.

W. C. ROCH, V. R. PENDERGRASS,

Assistant Examiners.

